A known superconducting motor apparatus serving as a superconducting apparatus is disclosed in JP2007-89345A (which will be hereinafter referred to as Reference 1). The superconducting motor apparatus disclosed in Reference 1 includes a superconducting coil generating a magnetic field when an electric power is supplied to the superconducting coil and a vacuum container defining a vacuum heat insulation chamber that accommodates the superconducting coil. The superconducting motor apparatus further includes a permeable yoke into which a magnetic flux of the magnetic field generated by the superconducting coil penetrates.
According to the superconducting motor apparatus disclosed in Reference 1, a heat penetration into the superconducting coil may suddenly occur depending on a practical use condition. In such case, the superconducting coil may be partially heated thereby deteriorating an output of the superconducting motor apparatus.
A need thus exists for a superconducting apparatus which is not susceptible to the drawback mentioned above.